History · Geology
About Naica Mine, Chihuahua
The Naica mine in Chihuahua, Mexico, is one of the world’s premier sources of gem-grade fluorite, transparent danburite, and — most spectacularly — the largest known natural crystals on Earth: the giant selenite gypsum crystals of the Cave of the Crystals (Cueva de los Cristales), discovered in 2000 at a depth of 290 m.
Geology
The deposit is a carbonate-replacement Pb-Zn-Ag mine in Cretaceous limestones, with gem pockets in Mesozoic skarn-replacement zones. The Cave of Crystals lies above a magma chamber where geothermally heated, anhydrite-saturated waters slowly grew selenite to extraordinary sizes (up to 11 m long, 1 m thick) over 500,000+ years.
Notable Minerals
Fluorite (gem-clear blue, purple, pink octahedra), danburite (gem-clear monoclinic prisms — exclusive Naica color zoning), calcite (large gem-clear rhombs), gypsum (selenite — the giant crystals), anhydrite, galena, sphalerite. Naica fluorites are highly coveted by gem collectors.
Collector Notes
Naica fluorite gem cabinet specimens command premium prices. The Cave of Crystals itself was sealed in 2017 to preserve the unique microenvironment; selenite specimens from the cave are unobtainable.
